The use of fossil fuel in gas turbine engines results in the combustion temperatures which in many application causes premature failure of the fuel injection nozzle end through oxidation, cracking and buckling. The fuel injection nozzle end must, therefore, be cooled to increase the design life of the fuel injectors.
Attempts have been made to cool the nozzle end and increase the life of such components. One such example, of a nozzle which has attempted to cool the end thereof is disclosed in U.S. Pat. No. 4,600,151 issued Jul. 15, 1986 to Jerome R. Bradley. The injector assembly includes a plurality of sleeve means one inside the other in spaced apart relation. An inner air-receiving chamber and an outer air-receiving chamber for receiving and directing compressor discharge air into the fuel spray cone and/or water or auxiliary fuel from the outside for mixing purposes. The air streams exit directly into the combustor zone wherein mixing with fuel and combustion occurs.
Another attempt to cool a nozzle is disclosed in U.S. Pat. No. 4,483,137 issued Nov. 20, 1984 to Robie L. Faulkner. This cooling system includes a central air passage and a twofold air flow directed by a secondary air swirl vane and a radially extending swirl vane. Each of the air streams exit directly into the combustion zone wherein mixing with fuel and combustion occurs.
Many of the cooling schemes of the past discharge the spent cooling air into the combustion chamber where it can adversely affect the combustion process. In the invention described herein the cooling air flow becomes a part of the combustion air prior to entering the combustion chamber. Therefore, its effect on the combustion process in general and NOx and CO emissions in particular is minimized. Furthermore, the quantity of cooling air is held to a minimum while effectively cooling the tip of the injector nozzle.